Audio-frequency converter apparatus, installation including said apparatus for treating subjects suffering from audio-phonatory and auditive-verbal disorders, and a method of using such an installation

ABSTRACT

Audio-frequency converter apparatus, in particular for treating subjects suffering from audio-phonatory disorders, the apparatus being suitable for generating, on the basis of an input audio frequency signal, a parametric signal for application via an electro-acoustic transducer to a person being treated. Included in the apparatus are an input amplifier, a first threshold detector connected to the output from the input amplifier and subtracting a threshold voltage from the voltage supplied from the amplifier, after rectification, a second threshold detector, likewise connected to the output from the input ampifier, and adding a voltage threshold to the signal from the input amplifier, after rectification, and having a time constant which is not less than the time constant of the first detector, a voltage controlled oscillator circuit connected to the output from the first threshold detector, and a (balanced) modulator whose two inputs are respectively connected to the outputs from the second threshold detector and from the oscillator circuit, and whose output provides the parametric signal.

This is a continuation of application Ser. No. 06/756,231 filed Jul. 18,1985, issued on Nov. 24, 1987 as U.S. Pat. No. 4,708,657.

The invention relates to an installation for audio treatment ofaudio-phonatory and auditive-verbal disorders present in certainsubjects, generally young children.

BACKGROUND OF THE INVENTION

It has been observed that some language anomalies (dysphasia) or writinganomalies (dyslexia) are related to dysfunction in the auditive-verbalperception of the subject, which dysfunction appears during thedevelopment of language in the subject.

Various solutions have already been proposed for reeducating saidperception. In particular, the Applicant's French Pat. No. 77 01 233,published under No. 2 377 189, suggests applying frequency modulation toan audio signal inversely to the modulation level of a pilot signal.

This prior installation has given only partial satisfaction, and thepresent invention seeks to improve it.

SUMMARY OF THE INVENTION

The present invention provides an audio-frequency converter apparatuscomprising, in combination:

an input amplifier;

a first threshold detector connected to the output from the inputamplifier and subtracting a threshold voltage from the voltage suppliedfrom the input amplifier, after rectification;

a second threshold detector, likewise connected to the output from theinput amplifier, and adding a voltage threshold to the signal from theinput amplifier, after rectification, and having a time constant whichis not less than the time constant of the first detector;

a voltage controlled oscillator circuit connected to the output from thefirst threshold detector; and

a modulator whose two inputs are respectively connected to the outputsfrom the second threshold detector and from the oscillator circuit, andwhose output provides the said parametric signal, e.g. for applicationto one or more electroacoustic transducers.

Preferably, the time constant of the first detector is about 0.05seconds and the time constant of the second detector is about 0.3seconds.

In a particular embodiment, both threshold detectors are connected tothe output of the input amplifier via respective level-adjusting units.

It is also advantageous for the thresholds of the two detectors to beindividually adjustable.

More particularly, the threshold of the first detector and/or thefrequency produced at rest by the voltage controlled oscillator areadjusted in such a manner that the frequency of the oscillator at restis close to the upper limit of the hearing range, which may vary withthe subject, and the threshold of the second detector is adjusted insuch a manner that the amplitude of the output signal from the modulatoris substantially nil when the oscillator is at its rest frequency.

According to other features of the invention:

the oscillator may be subjected to rapid frequency sweeping at a ratewhich is imperceptible to the human ear;

the oscillator may operate over a narrow frequency band whose averagefrequency is then a function of the output from the first detector; and

the oscillator may emit a signal whose harmonic content depends on theoutput from the first threshold detector.

The invention also relates to an installation including such apparatusand further including an input switch suitable for connection to a soundreader and/or to a microphone, and an output switch suitable forconnection to a sound reproduction chain or to a sound recording chain,the input switch being connected to the input amplifier and the outputswitch being connected to the output from the modulator.

BRIEF DESCRIPTION OF THE DRAWING

An embodiment of the invention is described by way of example withreference to the accompanying drawing, in which:

FIG. 1 is a circuit diagram of a converter per se in accordance with thepresent invention; and

FIG. 2 is a block diagram of an installation incorporating the FIG. 1converter.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, with reference 1 designates a portion of the apparatus,referred to as a "parameter converter" hereinafter, in this case theparameter being an audio-frequency signal. This signal has an input Eand an output S. Its input E is intended to receive a naturalaudio-frequency signal, in other words an input signal representative ofspeech or voice or music which may come from a normal person, from thesubject being treated, or from a source of music.

The natural input signal is applied to the input of a wideband amplifier10 having an output 11 which is applied to two level-adjusting units 12and 13 which are constituted by potentiometers in the present example.

The slider of the potentiometer 12 is connected to a first thresholddetector 2, and the slider of the potentiometer 13 is connected to asecond threshold detector 3.

The threshold detector 2 comprises a capacitor 21 having one plateconnected to the slider of the potentiometer 12 and having its otherplate connected to the anode of a diode 22 and to the cathode of a diode23. The cathode of the diode 22 is connected to the slider of apotentiometer 20 which is connected between a reference voltage ofpositive sign and ground and it is also connected to one plate of acapacitor 24 whose other plate is connected to the anode of the diode23. A resistor 25 is connected in parallel with the capacitor 24. Theanode of the diode 23 is also connected to one end of the resistor 26whose other end is connected to a plate of a capacitor 27 whose otherplate is connected to the slider of a potentiometer 20. The common pointbetween the resistor 26 and the capacitor 27 defines the output of thefirst threshold detector 2, which output is applied to avoltage-controlled oscillator (VCO) 4. Finally capacitor 28 is connectedbetween the slide of potentiometer 20 and ground.

The structure of the second threshold detector 3 is similar to that ofthe first. The slider of the potentiometer 13 is connected via acapacitor 31 to the cathode of a diode 32 and to the anode of a diode 33the diodes 32 and 33 are connected with polarities opposite those ofdiodes 22 and 23. The anode of the diode 32 is connected to the sliderof a potentiometer 30 which receives a reference voltage of positivesign at its terminals. The cathode of the diode 33 is connected to aplate of a capacitor 34 whose other plate is connected to the slider ofa potentiometer 30. A resistor 35 is connected in parallel with thecapacitor 34. The cathode of the diode 33 is also connected to one endof a resistor 36 whose other end is connected to a plate of a capacitor37 whose other plate is connected to ground. The common point betweenthe resistor 36 and the capacitor 37 constitutes the output from thesecond threshold detector. A capacitor 38 is connected between theslider of potentiometer 30 and ground.

The output from the VCO 4 is applied via a capacitor 40 to one input e₁of a modulator 5. The modulator receives two bias voltages V₁ and V₂.Its input e₁ is connected to the bias voltage V₁ via a resistor 50.

A second input e₂ of the modulator 5 receives the output from the secondthreshold detector 3. Finally, the outputs from the modulator 5,constitute the output terminals of the parameter converter 1.

The parameter modulator 5 can be a balanced modulator, in which case itsinputs e'₁ and e'₂ are AC grounded.

The person skilled in the art will understand that the first detector 2detects or rectifies its input signal, acting as a voltage doublerrelative to the threshold as defined by the potentiometer 20. With theillustrated polarities of the diodes 22 and 23 detection takes place forvalues below the threshold. When the input signal is greater thanthreshold, the output signal equals the threshold; when the input signalis lower than the threshold, the output signal is defined by the(negative) deviation (rectified and voltage doubled) between the inputsignal and the threshold. Consequently the output voltage from the firstdetector appears negatively with respect to the threshold as defined bythe potentiometer 20. A high value capacitor 28 prevents AC voltagesfrom appearing at the terminals of said potentiometer. Further, thecomponents 20 to 27 define a time constant which is about 0.05 secondsfor the first threshold detector.

In contrast, the second threshold detector 3 operates the other wayround. When its input voltage is below the threshold, the detector 3provides an output voltage having the same sign and value as thethreshold defined by the potentiometer 30.

When the input voltage of detector 3 is greater than the threshold, thenits output signal is comprised of the portion (rectified and voltagedoubled) of the input signal that exceeds the threshold. There thusappears across the terminals of the capacitor 37 a voltage which is thesum of the threshold voltage and the rectified voltage. The components30 to 37 are selected to give the second threshold detector a timeconstant of about 0.3 seconds.

The apparatus can be adjusted in various manners which will be describedin greater detail below. In normal operation, the threshold of the firstdetector 2 (and where necessary of the VCO 4) are adjusted so that thefrequency of the oscillator 4 when at rest is close to the upper limitof the hearing range, which may be predetermined as being 17,000 Hz, orwhich may be determined as a function of a particular subject's responseas analyzed using an audiogram. The threshold of the second detector isadjusted so that the amplitude of the output signal from the modulator 5is substantially nil when the oscillator 4 is at its rest frequency andthe voltage provided by the detector 3 is nil, since it could disturbthe adjustment.

In other words, modulator 5 multiplies the VCO output (applied to itsinput,) with the output signal (applied to its input e₂) of the secondthreshold detector 3.

At rest, the outputs of both threshold detectors 2 and 3 are at theirrespective threshold values, and modulator 5 delivers no signal(theoretically a signal at rest frequency, e.g. 17,000 Hz, of VCO 4, buthaving a zero amplitude due to the other input e₂).

Otherwise, voltage obtained at the output S of modulator 5 has afrequency which varies with the amount of modulation. This modulationfrequency goes down as a function of the modulation level, and with anamplitude which is exactly proportional to the amplitude of the inputsignal e₂.

In a particular embodiment, the diodes 22, 23, 32 and 33 are 1N 44 48type diodes. The potentiometer 20 is a 20 kohm potentiometer, thecapacitors 21, 24, and 27 are respectively 0.1, 0.22, and 0.1 microfaradcapacitors, and the resistors 25 and 26 are 0.1 Mohm resistors. Thecapacitor 28 is a 10 microfarad capacitor.

In the other threshold detector, the potentiometer 30 is a 20 kohmpotentiometer, the capacitors 31, 34, and 37 are respectively 0.47, 0.22and 0.1 microfarad capacitors, and the resistors 35 and 36 arerespectively 0.15 and 0.33 Mohm resistors. The capacitor 38 is a 100microfarad capacitor.

The oscillator circuit 4 may be an astable multivibrator preceded by anemitter-follower control stage.

When a fast frequency sweep is desired, an auxiliary oscillator 41 isadded to the VCO 4. The same applies when it is desired to operate overa frequency band rather than at a single frequency.

Finally, the balanced modulator 5 may be a 1496G type integrated circuitas manufactured by Motorola. Its terminal number 1 receives the outputfrom the second threshold detector. Its terminal number 10 receives theoutput from the oscillator circuit 4, which is interconnected with afilter device connected to terminal number 8. Terminal 14 is connectedto ground. The bias voltage V₁ and V₂ are applied to the inputs 5 and 12of the integrated circuit. Finally, the output from the integratedcircuit is given on its terminal number 6.

FIG. 2 shows a preferred application of the parameter converter oraudio-frequency converter 1 shown in FIG. 1 in an installation fortreating subjects. The converter is connected to an input switch CE andan output switch CS. The switch CE serves to connect the input E of theconverter 1 either to the read output from a magnetic head TM1 in acassette recorded MC1, preferably a high quality recorder, or else tothe output from a microphone M which should also be a high qualitymicrophone. Each of these inputs may be amplified via respectivepreamplifiers AM1 and M1.

The output S from the converter 1 is applied via the output switch CSeither to a two-channel sound reproduction chain AP, or else to therecording input of a magnetic head TM2 in a cassette recorder MC2, whichmay be the same recorder as the cassette recorder MC1.

It is advantageous for the switches CE and CS to enable a directconnection of the microphone M, the amplifier AP, and the recorder MC2.

To re-educate subjects suffering auditive-verbal dysfunction, it isdesirable for the sound reproduction chain AP to include, in knownmanner, means for individual level adjustments and for balancing eachchannel, associated with accurate measurement means, and outputs forelectro-acoustic transducers, e.g. loudspeakers T₁, T₂, for use with theleft and right ears, respectively, of the subject. It is alsoadvantageous to be able to supply the amplifier AP simultaneously withthe voltage E and S from the converter 1, with each level beingindependently adjustable. Finally, the ratio between the left and rightlevels may be different for E and S. Headphones are also provided toenable an operator to listen to the signal as reproduced, if so desired.All those adjustments are used in the example given hereinafter.

In the following, "comprehensible sounds" means natural sounds asavailable on input E of the converter (FIG. 2), and "parametric sounds"means processed sounds as available on output S of the converter 1.

An installation in accordance with the invention makes it possible toperform a method of treatment in which a mixture of comprehensiblesounds and of parametric sounds provided by the installation areinjected into each ear of the subject, with the ratio between thecomprehensible sounds and parametric sounds (that is, sounds producedafter processing a signal by the parameter converter) introduced intoone ear being different from that of the other ear. As explainedearlier, each of these ratios is independently adjustable.

It is possible by using such adjustments to avoid perception of anycomprehensible or parametric sound in either ear.

Practical use of the apparatus of FIG. 2, where a dyslexic subject isconsidered, by is described in the following example. Re-education takesplace in five stages over a period of four months and with at least twoone-hour sessions per week. The adjustments of the parameter converterover such a period is as follows:

Example (for treating dyslexia)

In the first stage, a "passive stage" in which the input signal maycomprise voice and music having a high level of high frequencies, theparametric sounds exhibit:

high amplitude with respect to natural sounds;

VCO rest frequency below the upper frequency threshold (i.e., athreshold above which sound becomes inaudible); and

maximum excursion of the VCO frequency (that is, the range offrequencies between which

the parametric sound is modulated.)

In the second stage, a "semi-active stage" in which the input signalcomprises music and "sibilants" (words with many "S" sounds) prerecordedfor repetition by the subject, the parametric sounds have the followingcharacteristics:

with respect to the music, adjustments are identical to those of stage1;

with respect to the "sibilant" words, the VCO rest frequency is abovethe upper audible threshold; the average amplitude of parametric soundsis the same as that of the natural sounds and the excursions of the VCOare reduced.

In the third stage, an "active stage", "sibilants" and words of textualmaterial are used, and the parametric sounds exhibit:

A VCO rest frequency above the upper frequency threshold;

low amplitude of parametric sounds with respect to natural sounds; and

low excursions of the VCO frequency.

In the fourth stage, texts and guided reading (with prerecorded tape)are used, and the characteristics of the parametric sounds are identicalto those the preceding stage.

In the fifth stage, guided reading and free reading exercises are used,and the parametric sounds have essentially a zero amplitude with respectto the natural sounds.

In the above example, it is supposed that the oscillator circuit 4generates a pure frequency, together with optional harmonics thereof.

It is possible to use numerous variants of the present invention, inparticular concerning the oscillator circuit. It is thus possible tovary, for example:

the preferred frequencies of pink noise produced by the oscillator, ormore precisely by an appropriate low frequency generator;

the wobble characteristic of a wobbling signal, i.e. a signal subjectedto frequency sweeping;

the form factor of a squarewave signal produced by the oscillator; and

the harmonic content of the signal produced by the oscillator.

Moreover, it is also possible to simultaneously utilize a plurality ofsignals which are either in musical harmony or cover a narrow frequencyband. The average frequency and the amplitude are then modified by theparameter converter as described above.

These variant embodiments make it easier to cover the resonantfrequencies of the subject's inner ear within the band transmitted bythe oscillator circuit.

The case in which it is desired to emit noise covering a band offrequencies in a permanent manner deserves special attention. It may bedifficult to emit noise of this kind and to subject it to the variousmodulations proposed by the present invention. In such a case anoscillator circuit is used which emits a single sound at a time, whichis in addition subjected to frequency sweeping over the prescribed band.This frequency sweeping may take place very rapidly, for example,200,000 times per second so that the ear cannot perceive the sweepingand has the impression that the band is constantly occupied.

We claim:
 1. A device for treating auditory disorders, comprising aparametric converter for converting from an audio signal supplied tosaid parametric converter at an input thereof to a parametric signalcorresponding to said audio signal, said parametric signal being outputfrom said parametric converter at an output thereof, said parametricconverter comprisingfirst and second threshold detector means, eachoperatively connected to said input of said parametric converter, eachfor rectifying said audio signal with respect to a respective thresholdand polarity of said audio signal, and each providing a respectiveoutput with a respective time constant, said time constant of saidoutput of said second threshold detector means being greater than saidtime constant of said output of said first threshold detector means, avoltage controlled oscillator receiving as an input said output of saidfirst threshold detector means and providing an oscillating outputhaving frequency that decreases with increase in said output of saidfirst threshold means, modulator means for receiving as a first input asignal corresponding to said oscillating output of said voltagecontrolled oscillator and as a second input said output of said secondthreshold detector means, and for outputting as said output of saidparametric converter said parametric signal oscillating with saidfrequency of said first input to said modulator means with an envelopeamplitude that increases with increase in said second input to saidmodulator means.
 2. The device of claim 1, comprising combining meansfor simultaneously providing as an auditory signal to an ear of apatient with said auditory disorder a combined audio signalcorresponding to a mixture of said parametric signal and audio signal,and said audio signal corresponds to normal sound of at least one ofmusic and voice.
 3. The device of claim 2, said combining meansincluding means for effectively changing the ratio of said parametricsignal to said normal sound in said auditory signal for said ear of saidpatient during a treatment of said patient for said auditory disorder.4. The device of claim 2, comprising means for providing a respectiveone of said auditory signals to each of two ears of said patient,wherein said ratio of said parametric signal to said normal sound insaid mixture of each said combined signal provided as the respectiveauditory signal to each of said ears of said patient can be variedindependently during treatment for said auditory disorder.
 5. The deviceof claim 1, each said threshold detector means comprisinga respectivefirst potentiomenter connected at a first terminal to ground and at asecond terminal operatively to said input of said parametric converter,a respective first capacitor connected at a first end to a wiper of therespective first potentiometer, a respective second potentiometerconnected at one end to ground, a respective first diode connectedbetween a wiper of the respective second potentiometer and a second endof the respective first capacitor, a respective second diode connectedat a first end to said second end of the respective first capacitor, arespective first resistor connected at a first end to a second end ofthe respective second diode, and at a second end to said output of therespective threshold determining means, a respective second resistorconnected at a first end to said first end of the respective firstresistor and at a second end to said wiper of the respective secondpotentiometer, a respective third capacitor connected at a first end toground and at a second end to said wiper of the respective secondpotentiometer, and a respective fourth capacitor connected at a firstend to said output of the respective threshold detector means.
 6. Amethod for treating an auditory disorder of a patient, comprisingproviding to the ear of a patient an audio signal corresponding at leastto a parametric signal in turn corresponding to an audio-frequency soundsignal intended to be heard by the patient, said providing includinggenerating said parametric signal based on said audio-frequency soundsignal, wherein said providing of said parametric signal is such thatsaid parametric signal decreases in frequency from a predeterminedmaximum frequency as said audio-frequency sound signal increases inamplitude with respect to a first threshold and polarity, and increasesin amplitude from a first predetermined value with increase of saidelectronic signal with respect to a second threshold and polarity. 7.The method of claim 6, wherein said providing is such that said firstpredetermined value is operatively zero.
 8. The method of claim 6,wherein said audio signal provided to an ear of said patient includestwo audio components, a first of said audio components corresponding tosaid audio signal corresponding to said parametric signal, and thesecond of said audio components corresponding to said audio-frequencysound signal.
 9. The method of claim 8, wherein the ratio of said twoaudio components in said audio signal provided to an ear of said patentis varied during said treatment.